Construction material



May 12, 1931. G. c. DOUGLAS CONSTRUCTION MATERIAL Filed Jun@ 25, 1928Patented May 12, 1931 UNITED STATES PATENT OFFICE GORDON U. DOUGLAS, OFCOVINA, CALIFORNIA, ASSIGNOR OF ONE-DLALF TO DAVID G.

SMALL, OF LOS ANGELES, CALIFORNIA CONSTRUCTION MATERIAL Applicationfiled June 25,

This invention relates to a new and novel construction material.Particularly, the invention relates to a construction material in theform of tile blocks or panels having acous- 5 tic properties so thatsaid blocks, tile or panels may be used, in construction work for sounddeadening or sound absorbing purposes as well as a structural wallcovering. Briefly, the construction material embraced 10 by thisinvention comprises a structural base having a layer of acoustic orsound absorbing material bonded to a surface thereof so as to form aunitary body capable of being fastened to walls or ceilings.

An object of this invention is to disclose and provide a unitarystructural material which is strong, light in weight and having soundabsorbing characteristics.

Another object is to disclose and provide a construction material havinga structurally strong backing and a covering of relatively light andporous sound absorbing material having cavities on its outersurface.

Other objects and advantages, uses and functions of this invention willbe 'ap arent to those skilled in the art from the ollowing detaileddescription of the structural material embraced by this invention andone preferred method of making the same.

It has been well known for some time that reverberation of sound inhalls, auditoriums and other edifices could be materially reduced'orsubstantially eliminated by introducing sound absorbing materials intosaid rooms, halls or auditoriums. Very often the walls of such roomshave been covered with porous materials or fibrous materials having anopen texture so as to break up the continuity of the wall and therebyassist in reducing the amount of reverberation and in absorbing excesssounds. The first difficulty encountered has been mechanical, that is,the difliculty of placing or fastening such sound absorbing oracoustical bodies on walls or ceilings. The only materials which can bereadily applied are fiber boards having a loose open texture as theseboards can be ob tained in fairly large sheets and may be readilyattached to the walls or ceilings by means of nails, screws and thelike.

1928. Serial No. 288,064.

None of the materials heretofore to possess acoustical propertiessuitable for the purposes hereinabove described have i and C of themusical scale by tests have shown that all of the acoustical materialsnow on the market (including fibrous materials, cementitious materials,and the like) absorb the higher or instrumental notes with much greaterefficiency, than those pitches which are used in human speech. Thischaracteristic leads to the result that auditoriums, for example, may beconstructed and properly insulated against sound reverberations and theresults therein as far as instrumental music is concerned andparticularly the higher notes thereof, will be very good, but when suchauditorium is used for thepresent-ation of stage plays or other purposesin which the human voice plays an important part, it is found thatreverberation still occurs and it is impossible to clearly hear andunderstand the speakers in variousportions of the auditorium.

I have discovered that a porous material having cavities on its outersurface ranging in size from about one inch to 0.02 inches and having anaverage opening of from about 0.2 to 0.3 inches will substantiallyuniformly absorb sounds of varying pitches.

A material of this nature may be readily produced from 'cementitiousmaterial by adding gas-forming ingredients to a cementitious materialand then casting or molding a block or tile therefrom, the gas formingingredients causing porosities in the cementitious material. After thismaterial has set, these porosities may be exposed by scraping thesurface of the tile panel or block so as to remove the excess ofcementitious material which may have a tendency to envelope or cover thepores.

A cementitious material of the above described nature, however, can notbe used alone to any advantage as it is relatively weak structurally andin view of the fact that panels or blocksof such material need not beover one, or at most, two inches in thickness, such thin blocks can notbe fastened to walls or ceilings without undue breakage or loss.Furthermore, the plastic or semi-fluid composition utilized making upthe tile is of suclr fluidity that it can not be applied to a' wall inthe form of a plastic .or fluid mixture and allowed to set on theerected wall,

as the composition runs off and can not be troweled as this liberatesthe gases formed by the gas-forming constituents and reduces the mass tosuch density that the porosity of the finishedsurfacing is ineffective.It will be readily understood that if a body of fluid cementitiousmaterial containing gasforming constituents is agitated or worked ortroweled in any manner, such working or troweling wouldcause the gas tobe freed from the cementitious envelope and the entire tile will containnot only a much smaller proportion of pores, but such pores as are stillleft in the material would not be at'the sur face where they are of anyuse, but in the bottom or deepest portions of the cementitious mass.

By means of this invention, it is possible to produce a structuralcementitious acoustically sound absorbing material which is not onlyeasily applied and fastened to walls and ceilings, but uniformly absorbsvarious sounds or pitches.

In describing one preferred form of this invention, reference shall behad to the attached drawings'in which:

Figure 1 is a plan view of one portion of a tile or panel showing theporous surface which is exposed to the reception of sounds.

Figure 2 is a vertical sectiontaken through such tile shown in Figure 1.

In manufacturing a tile embraced by this invention by. one preferredmethod, a structural body or base such as, for example, a plaster board,wood panel, fibrous board, or chip board or other like material which isnormally employed-in the" form of sheets and which is adapted toreinforce the tile, such as the plaster board 10 in the drawings, islaid withm a suitable mold or upon some horizontal or substantiallyhorizontal surface and a cementitious composition containing gas-formingingredients then mixed with water to produce a plastic or semi-fluidmixture of the desired consistency and such plastic or semi-fluidmixture placed or poured upon the upper surface of the structural base10. The cementitious material is applied to the structural base 10 to adesired depth or thickness, for .example, one inch and is gently"troweled or leveled, for example, by means of a straight edge restingincontact with the structural base 10 so as to insure a thorough bondbetween the base and the cementitious material. If desired, thestructural base 10 may be treated so as to key into the cementitiousmaterial and for this purpose, various forms of lath board now on themarket may beemployed with advantage. After the cementitious materialhas set in contact with the structural base 10, the upper surface 11ofthe cementitious body 12 may be lightly scraped or otherwise treatedso as to expose the cavities or porosities 13. It will be understoodthat some of the porosities 13 will be formed and exposed prior to saidscraping or exposing operation, but an additional number of porositieswhich may be covered by thin film of the cementitious material 12 arethus exposed by the scraping operation. In

. divided calcium carbide capable of reacting with water or. othergas-forming constituents of similar nature.

In addition to the cementitious material. and the gas-formingingredients the composition may contain fibrous matter or a filler. Asuitable filler found to be very suitable for this work shouldpreferably be of a porous character,- for example, diatomaceous earth.Itwill be understood that various retardation or accelerating materialsmay also be added to the composition depending somewhat upon thecharacter of the cementitious material, the character of the gas-formingingredients or the plasticity or fluidity of the mixture so that theresulting porosities may fall within the limits of size givenhereinabove.

One composition which has been used with great advantage may be formedby mixing about 85 to 95% by volume of ordinary cast- .ing plaster, 2 to8% by volume of magnesium carbonate and 2 to 8% by volume 0 aluminumsulfate. When this mixture is rendered plastic or semifluid by theaddition of water and then quickly poured or placed upon a structuralbase, the aluminum sulfate dissolves in the water and acts upon themagnesium carbonate forming a multiplicity of areas throughout the massin which carbon dioxide is being liberated. This produces a porous mass,the carbon dioxide being trapped within the body by the cementitiousmaterial. Three to eight percent by weight of a fibrous material such ashemp, hair or asbestos may be'added to the mixture so as to render itmore resistant to shock. A pigment or other coloring material may alsobe added to the composition so as to form a body of pleasing color andin harmony with the building or interior in which the finished tile orpanel is to be used.

It has been found that with the above composition the use of a retarderis not required, the gas-forming ingredients preventing a too rapid setof the gypsum. If, however, a retarder is desired, it may be added tocasting plaster, or'a hard wall gypsum plaster may be used.

In order to facilitate the fastening of the pre-formed tile or panelshereinabove described to walls or ceilings, the structural base 10 maybe provided with means adapted to cooperate with fastening means bymeans of which the finished tile or panel maybe attached to the walls.For example, the structural base 10 may be provided with perforationsor. openings 15 such perforations or openings being placed near theedges of the tile so as to allow nails, screws, or other fastening meansto be easily passed therethrough. During the molding and formingoperation hereinabove described, pegs or other cores may be placed inthe openings 15 extending to the surface 11 of the finished body so thatafter casting or molding the panel the pegs or cores may be withdrawnleaving an opening through the finished tile.

and thereby facilitating the location in openings 15. Screws may then beplaced in the openings extending through the body 12 of the tile andcoinciding with the openings 15 in the structural base thereof andthe'completed tile fastened to the wall or ceiling by means of saidscrews. The openings left in the cementitious body above the opening 15may later be filled up by pointing or filling with a suitably coloredcementitious composition. i

Instead of the openings 15 tie wires or other fastening means may beattached to the structural base 10 extending for somedistance beyond thelower or back surface of the finished tile so as to enable the tile tobe fastened to ceilings or other portions of a structure. Numerouschanges and modifications may be made in the fastening means withoutdeparting from the invention. For example, the tile embraced by thisinvention may be applied to a brick, hollow tile or rough plastered wallby spotting the wall and/or the backs of the tile with a gypsumcomposition, lime mortar or other cementitious material capable ofthoroughly adhering to both the wall and the structural back- .ing ofthe tile, and then merely placing the tile in contact with such spottedwall, as by pressing the tile into place.

surface, may be treated with a solution obtained by dissolving boricacid in aqueous ammonia, or with a solution containing stearic acid andsodium carbonate.

It will be seen, therefore, that by means of this invention a structuralbody is produced having considerable strength, althrough theacousticalmaterial itself is relatively weak and brittle. The tiles maybe readilyplaced and fastened to walls and ceilings and the peculiar character ofthe surface developed by the compositions hereinabove described enablesthe material to absorb various pitches or notes in a relatively uniformmanner. Heretofore it has been impossible to utilize a composition'ofthe character described herein in detail for sound proofing or soundabsorbing surfaces, whereas by means of the tile herein described, suchsurfaces are made available and very desirable results may be obtained.

I claim:

1. As an article of commerce, a preformed acoustic tile comprising, abase of plaster board, a layer of porous cementitious. material havingcavities exposed on its surface bonded to one side of said base duringthe setting of the porous cementitious material and provided with meansadapted tocooperate with fastenin means to attach said tile to walls andceilings.

2.. As an article of commerce, a preformed sound absorbing constructionmaterial comprising, a base of structural material, a layer of porousgypsum composition having cavities ranging from about 0.02 to 0.8 inchesin averageidimensions exposed on its surface and bonded to one side ofsaid base during the setting of the porous gypsum composition andprovided with means adapted to cooperate with fastening means to attachsaid tile to walls and ceilings.

3. As an article of commerce, a preformed sound absorbing constructionmaterial in the form of panels and tiles comprising, a base of plasterboard and a layer of porous cementitious material having cavitiesexposed on its surface, bonded to one side of said plaster board duringthe setting of said porous cementitious material. 1

4. As an article of commerce, a preformed sound absorbing constructionmaterial comprising a base of structural material and a layer of porouscementitious material having cavities exposed on its surface, saidcementitious material being bonded to one side of said base during thesetting of the porous cementitious composition.

Signed at Los Angeles, California, this 13th day of June, 1928. 4 v

GORDON O. DOUGLAS.

